Air compressor



Feb. 8, 1966 v. J. HUBER. ETAL AIR COMPRESSOR 2 Sheets-Sheet 1 Filed June 21, 1963 INVENTORS VINCENT J. HUBE JAMES S. McCARTN ATTORNEYS Feb. 8, 1966 v HUBER ET AL 3,233,554

AIR COMPRESSOR Filed June 21. 1963 2 Sheets-Sheet 2 101% Ame X ne 1") N03 INVENTORS 7- 7+ VINCEN HUBER |7| I73 BY JAMES S. ARTNEY & kn 20M ZVLWrW ATTORNEYS United States Patent 3,233,554 AIR COMPRESSOR Vincent John Huber, Shakopee, and James S. McCartney,

St. Paul, Minn, assignors to Aero Spray, Inc., Minneapolis, Minn., a corporation of Minnesota Filed June 21, 1963, Ser. No. 289,588 17 Claims. (Cl. 103157) This invention is directed to new and novel improvements in a pump unit that can be used either as a double acting air compressor or a vacuum pump. More particularly this invention is directed to a new and novel air compressor having a pair of pistons mounted in a cyclinder for both translatory and rotary movement together with new and novel drive mechanism for simultaneously reciprocating and rotating said pistons.

In double acting air compressors of the prior art a set of pistons have been mounted for only reciprocal movement and as a result undue stresses and wear exist, plus having heavy power requirement. This results in such prior art air compressors heating relatively rapid and precluding them being continuously operable over long periods of time. In order to obviate the problems of the aforementioned nature this invention has been made.

" One of the objects of this invention is to provide a double acting air compressor having a driven pair of pistons that are simultaneously rotated and reciprocated. Another object of this invention is to provide a new and novel floating eccentric drive connection between motor means and the pair of pistons of the double acting air compressor. Still another object of this invention is to provide a new and novel fluid seal between the cylinder and pistons of the double acting air compressor that minimizes wearing of the pistons and the seal members. A further object of this invention is to provide a double acting air compressor that may be operated continuously at relatively high efiiciencies but still at the same time provide a substantial volume of air output with a smaller and more compact compressor unit than that achieved in the prior art.

Other and further objects are those inherent in the invention herein illustrated, described and claimed, and will become apparent as the description proceeds.

To the accomplishment of the aforegoing and related ends this invention then comprises the features hereinafter fully described and particularly pointed out in the claims. the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

The invention is illustrated by reference to the drawings in which corresponding numerals refer to the same parts and in which:

FIGURE 1 is a side view of the first embodiment of the air compressor of this invention together with a portion of the piston drive structure, said view showing the piston assembly in dotted lines in the mid-portion of the piston stroke.

FIGURE 2 is a longitudinal cross sectional View generally taken along the line and in the direction of arrows 2-2 of FIGURE 4 other than no portion of a piston assembly or piston assembly drive structure is illustrated;

FIGURE 3 is a top view of a piston assembly, the angles of inclination of the piston surfaces being exaggerated;

, FIGURE 4 is a transverse cross sectional view generally taken along the line and in the direction of the arrows 4-4 of FIGURE 6 to more fully illustrate the valving and the construction of the manifold plate;

FIGURE 5 is a transverse cross sectional view of the air compressor and the piston drive structure, said view eing generally taken along the line and in the direction of arrows 55 of FIGURE 1;

FIGURE 6 is a longitudinal cross sectional View of an air compressor of this invention showing the piston assembly and drive structure, said view being generally taken along the line and in the direction of arrows 66 of FIGURE 5 other than that the piston assembly and piston drive mechanism is in advance of the position illustrated in FIGURE 1;

FIGURE 7 is an enlarged fragmentary cross sectional view further illustrating the replacement sleeve subassembly and the mounting thereof, the radial clearance between the metal and plastic sleeve being exaggerated; and

FIGURE 8 is a longitudinal cross sectional view, other than a portion of the piston assembly, of a second embodiment of the invention illustrating the principles of this invention for a two stage compression unit, the exterior fins not being illustrated.

Referring now in particular to FIGURES 1 and 2 the air compressor of this invention, generally designated 10, includes a generally tubular housing 11 having exterior fins 12 and a central transverse bore 14 that opens into the hollow interiorlS of the housing, the housing being made of, for example, aluminum. On either longitudinal axial side of the bore 14 the housing interior is enlarged at 15a to form a shoulder.

Mounted in each of the diametrically enlarged portions 15a intermediate bore 14 and the respective end of the housing is a removeable fluid seal subassembly that includes a retainer ring 13 adjacent the respective end plate, a metal mounting sleeve 19 having a radially extending flange, sleeve 16 and a metal sleeve 17. Intermediate each of the sleeves 16 and sleeves 17 there is provided a wiper ring 18. Preferably sleeve 16 and ring 18 are made of a resilient plastic material such as polytetrafluoroethylene and sold under the trademark of Teflon. As may be noted in FIGURES 2 and 7 the inside diameter of the Teflon sleeve is slightly less than the inside diameter of the sleeve 17. Further it is to be noted that the wiper ring has a generally radially extending annular portion 1% retained in abutting engagement with and between sleeves l6 and 1'7, and an axially outwardly bent inclined portion 18a overlaying the adjacent axial portion of sleeve 17. The purpose of providing a wiper ring of this configuration will become more apparent hereinafter.

Each metal sleeve 17, wiper ring and Teflon sleeve are mounted in the respective mounting sleeve with the Teflon ring abutting against the mounting sleeve flange, the inside diameter of mounting sleeve radial flange being substantially the same as the minimum diameter portion of bore 15. The inside diameter of the retaining ring is approximately the same as the aforementioned diameters and accordingly the retainer ring serves to replaceably retain the mounting sleeve in abutting relationship with the shoulder 15a and members 1648 in the above described relationship in the mounting sleeve. If desired the mounting sleeve can be provided with a small axial annular flange that is bent to a radial position to abut against sleeve 17 to retain it in an assembly condition as shown in FIGURE 7.

An end wall 21 and a cylindrical manifold plate 20 are secured to one axial end of the housing by screws (not shown), the end wall being located intermediate the housing and said manifold to abut against one axial end of the housing. The manifold plate also is provided with exterior fins. On the opposite axial end of the housing there is likewise mounted a second cylindrical manifold plate 22 and an end wall 23. Each manifold is provided with an outlet chamber 26 and an inlet chamber 27, each of said chambers being somewhat semicircular in trans- Patented Feb. 8, I966 verse cross section and separated from each other by an integral diametric rib. Radially extending grooves fluidly connect the outlet chambers to fluid passageways Zia and 23a respectively in the respective end plates 21, 23, said passageways being in fluid communication with the bore 11b that extends axially across the housing. An outlet boss 110 is integrally formed with the housing, said boss having an aperture that extends to generally bisect bore 111). An outlet line 29 is connected to the boss lie for conveying pressurized air from the bore 11b to a reservoir (not shown) or to the object utilizing pressurized air.

Radially extending grooves likewise fluidly connect the inlet chambers to ports 21b and 23b respectively of the respective end plate, said ports in turn being in fluid communication with theaxially extending bore 11d formed in the housing wall diametrically opposite bore lib. An inlet boss lie of the same construction as boss He has a radially extending bore that opens to bore sections lid to place it in fluid communication with the ambient atmosphere.

A port lie is provided in the end wall 21 to establish fluid communication between the variable capacity cylinder chamber 31 of the tubular housing and the adjacent outlet chamber 26 (see FIGURE 6). An elongated leaf valve 34 of spring steel has one end connected to the end wall 21 at 35 and the opposite end overlying port 210, the leaf valve being located within the chamber 26 and resiliently urged to a closed position. Likewise there is provided in the outlet chamber of the manifold 22 a leaf valve 34 overlying port 2% of end plate 23. The purposes of providing the aforementioned leaf valves will become more apparent hereinafter.

Each of the end plates 21 and 23 has a generally rectangular recess opening to the hollow interior of the housing 11 (adjacent variable end cylinder chamber 31 and 32 respectively). An elongated leaf valve 37 is pivotally connected at 38 to be within the respective recesses of the end walls to overlie the ports 21d and 23d of the end plates 21 and 23 respectively. Due to the aforementioned mounting the leaf valve 37 can resiliently bend to extend into the hollow interior of the housing to permit fluid communication between the interior of the housing and the adjacent inlet chamber 217 and also permit the pistons 42 and 4-3 to be moved closely adjacent the end plate at the respective end of the piston stroke.

Mounted within the interior of the tubular housing is a double piston assembly generally designated it) (see FIGURES 3, 6 and 7), the axial length of said assembly being of a dimension A that is shorter than the axial length of the interior of the housing by a dimension X (see FIGURE 6). The piston assembly includes a connecting rod 43. having the cylindrical piston 42 at one end and the second cylindrical piston 4-3 at the opposite end, the outside diameters of said pistons being of a dimension to form a sealing fit with the inner peripheral surface of the respective Teflon wiper ring 18 as will be set forth hereinafter. As may be noted from FIGURES 1 and 6 the piston assembly at) is mounted within the tubular housing to be reciproeated in an axial direction (either arrow 44 or 47), FIGURE 6 showing the piston assembly at one axial end of the piston stroke. The maximum length of the piston stroke is of a dimension X.

In order to drive the piston assembly there is provided a drive mechanism generally designated 55 (see FIG- URE The drive mechanism includes a motor 56 that is bolted to an annular mount 57 formed integral with the tubular housing 11. The annular mount is located diametrically opposite from bore 14 and has the motor shaft 56a extended thereinto. Also the interior of the annular mount opens into the hollow interior of the tubular housing diametrically across from bore 14.

Keyed to the motor shaft is a stud mounting shaft 59 which has an integrally formed short stud shaft ea eccentrically located with reference to the central axis of rotation (M.A.M.A. of FIGURE 3) of the motor shaft but extending axially on the opposite side of shaft 59 from the motor shaft. Connected to the stud shaft to rotate therewith is a ball bearing 61 having an inner race 61a, and an outer race 61b of a diameter to have he outer circumferential portion thereof bear at all times against the adjacent axial surfaces of the pistons 42 and 43. To be noted is that the eccentrically located cam (ball bearing) is located between motor and the connecting rod and does not abut against the connecting rod.

As will become more apparent hereinafter the piston assembly as it is drivenly reciprocated by the aforementioned drive structure, it is also rotated about its central longitudinal axis P.A.P.A. In the preferred construction the motor shaft axis M.A.M.A. lies in a common plane with axis P.A.--P.A. but at right angles thereto as indicated by FIGURES 3 and 6. In such an event the outer axial lines of the peripheral surface of the bearing outer race are parallel to axis P.A.P.A. while the axial face 42a of piston 42 adjacent the bearing is frustoconical in shape and forms an angle A with the piston assembly axis (in the range of 89.8 and preferably in the range of 88.5-89.5); and the surface 43a is also frusto-conical in shape and forms an angle B with said piston assembly axis (in the range of 10090.2 and preferably in the range of 91.5 90.5 It is preferred that angle A be substantially 89 and thus in the plane of the axes P.A.P.A., M.A.M.A. the lines of intersection of said plane with the surfaces 42a, 43a on the same diametric side of the piston assembly are parallel to one another but ofiset 1 from being 90 to the piston assembly axis, provided angles A and B are the preferred angles.

Another but less desirable way of accomplishing substantially the same result as that achieved by the construction of the preceding paragraph is to construct the pistons so that surfaces 42a, 43a are parallel to one another and rare at right angles to axis P.A.P.A. but offset the motor so that the motor axis M.A.-M.A. is in the same plane as the piston assembly axis but forms an 89 angle therewith instead of 90 as described in the preceding paragraph, assuming the preferred angles are used. However it is to be understood that the same ranges are applicable to the offsetting of the motor axis.

The structure of the first embodiment of the air compressor of this invention having been described, the operation thereof will now be set forth. For purposes of facilitating the description of the operation it will be assumed that the piston assembly and piston drive member are located in the position illustrated in FIGURE 1 and that the motor shaft is rotated in the direction of the arrow 75 about motor shaft axis M.A.M.A. Rotating the motor shaft in the aforementioned direction causes the piston drive member to move the piston assembly in the direction of arrow 43 from the position illustrated in FIGURE 1 toward the position illustrated in FIGURE 6. As the piston assembly is being reciprociated in the direction of arrow 48 the movement of the cam from the FIG- URE 1 position constantly moves a different circumferential portion of the stud shaft 60 and the inner race to be located most closely adjacent piston 42 while at the same time forcing the piston to move in the direction of arrow 48. Further since the initial movement of the eccentric shaft tii) from the FIGURE 1 position progressively raises the center transverse axis thereof, the cam outer race constantly engages the piston axial surface 42a at progressively higher elevations while exerting a greater pressure against piston 42 than piston 43. Thus the greatest pressure is exerted on the outer radial portion of the surface 42a since it is inclined at about a one degree angle, the angle being exaggerated in FIGURE 3. This results in a rotary motion being positively imparted to the piston assembly to cause it to rotate in the direction of arrow 76 while the assembly is being reciprociated.

However the friction between the drive member and the piston assembly is minimized since the outer race is free to rotate at the same angular rate or corresponding angular amount as the piston assembly and rotate relative the inner race. This minimizes the friction between the piston drive structure and the piston assembly.

Further, the point of contact between the outer race and the piston surface is constantly changing as a result of the movement of the shaft 60 through an annular path, the bearing 61 being ec-centrically mounted and the inclination of the motor axis relative the piston surfaces that are adjacent said bearing. This results in the bearing through a period of different increments of time abutting against an annular portion of the adjacent axial surfaces of the piston rather than being concentrated along one straight line on said surfaces as would be the case if the pistons were not rotated. That is if the piston assembly did not rotate, the hearing would gradually peen a rectangular area on each piston surface 42a, 43a respectively, however due to the rotation of the piston assembly the contact of the cam with said surfaces is spread across an annular portion of said surfaces and accordingly wearing is minimized. Additionally the positive rotation of the piston assembly distributes the load from the bearing over the entire diameter of the connecting rod as it turns so that wear of the piston-s and sleeves is even and is reduced by a factor of about 50 to 100 depending upon the size of the compressor.

Further the continuous rotation of the piston assembly inside the Teflon sleeve and wiper ring causes any foreign matter which might tend to either scratch the respective piston or wear a groove in the Teflon sleeve or wiper ring to be forced to move along until it is either absorbed into the Teflon and buried or else passes through the, cylinder chambers and out of the compressor.

With reference to each wiper ring they, are formed from annular rings having inside diameters substantially less than the pistons and then bent to form 13,11 inclined portion 18a and radial portion 18b. The inside diameters of the inclined portions and the sleeves 16 are such that under normal operating conditions for a piston of, for example about 3% inches, the piston is solely supported by the inclined portion and does not contact the sleeves 16, there being a nadial clearance of about .08.10 inch between the pistons and the sleeves 16. As the surfaces of the inclined portions that contact the pistons wear away, the inclined portions through their memory bend to more nearly approach a straight line continuation of radial portions 18b.

Accordingly the wiper ring has a portion extending radially and the remaining portion is angularly inclined and is resiliently urged into engagement with the adjacent piston so that the inner angular edge wears to a thin edge which wipes foreign material off the piston while it is reciprocated and at the same time forms only a relatively thin contact edge (for example, .02 inch thick) that con: tacts the piston to thereby minimize heating. That is in normal operation, the pistons only infrequently contact the Teflon sleeves. Further there is formed a more positive seal when air is being compressed in the respective cylinder chamber, but whenair is being drawn into the respective chamber it permits slight flexing of the wiper ringinclined portion to dislodge any material on the portion of the wiper ring adjacent the piston.

Also to be mentioned. is that the Teflon sleeve and wiper ring are held in place by a replaceable metal mounting sleeve. Thus the entire assembly of the Teflon sleeve, wiper ring, metal sleeve and mounting sleeve can be replaced relatively easily without tearing down the compressor. The importance of the replaceable metal sleeve, Teflon sleeve, Teflon wiper ring and mounting sleeve (preferably of aluminum) is that such an assembly will expand with heat at the same rate as aluminum housing of a compressor, thus increasing tolerances and reducing friction rather than vice versa. As a result the compressor can be run with smaller motors with a magnitude of minus 6 70% since in prior art compressors friction is the greatest cause of requiring additional horse power.

As piston 42 is moved in the direction of the arrow 48 it causes suflicient compression of air in cylinder chamber 31 to overcome the resilient action of the adjacent valve 34 plus the pressure of air in the adjacent manifold chamber 26 to flex said valve from a closed position closing port 21c to an open position permitting the flow of pressurized air from chamber 31, through port 210 into the exhaust chamber 26, and thence pass from the exhaust chamber through port 21a and bore 111; to the bore of the outlet boss 11c.

At the same time that piston 42 is compressing air in chamber 31, the movement of piston 4-3 away from end plate 23 produces a suflicient reduction of pressure in cylinder chamber 32 so that the adjacent leaf spring 34 through its resiliency action returns to a position closing port 230 and leaf spring 37 to flex to open port 23d and thereby draw air from the inlet chamber 27 of manifold 22 into cylinder chamber 32. When the piston assembly is being moved in the direction of arrow 47, through appropriate flexing of the valves on the end walls 21 and 23, air is drawn into cylinder chamber 31, and air in chamber 32 is compressed to exit through the exhaust chamber of the manifold 22 and thence through bore 11b and the exhaust line 29. It is to be noted that the intake and exhaust leaf valves at each end of the tubular housing are located on a common plate so that merely by turning the plates 21 and 23 180 about axis P.A.-P.A., the compressor may be utilized as a vacuum pump.

Further rotation of the motor shaft to a position angularly in advance of that illustrated in FIGURE 6 results in the cam bearing against a progressively lower portion (in vertical elevation) of the piston 43 and thereby continues to cause the piston assembly to rotate and be reciprocated, while after the motor shaft is rotated still another 90 greater pressure is again exerted on piston 42 than piston 43. This causes the piston assembly to be again moved in the direction of arrow 48.

The operation of the first embodiment of this invention having been described, the structure of the second embodiment will now be set forth. The second embodiment of air compressor, generally designated includes a tubular housing 101 that advantageously is provided with exterior fins (see FIGURE 8). The tubular housing includes a maximum diameter bore 102 that opens into a smaller diametric bore 103, bore 102 being of a substantially greater axial length than bore 103. A central transverse bore 104 opens through the side wall of a housing atthe midportion of the hollow interior of the housing.

An end wall 105 and a cylindrical manifold plate 106 are secured to one axial end of the housing, the end Wall being located intermediate the housing and said cylindrical manifold. The manifold plate has a recess formed therein which in conjunction with the end wall forms a chamber 108. A port 107 is provided in the end wall to establish fluid communication between the variable capacity and chamber 114 of the tubular housing and the chamber 108. An elongated leaf valve 118 of spring steel has one end connected to the end wall at 119 and the opposite end overlying the port 107. The cylindrical manifold is also provided with a bore 120 for fluidlycom' necting the chamber 108 to the connecting line 121.

The opposite axial end of the housing likewise has an end wall 124, a cylindrical manifold 125, that in conjunction with end wall 124 provides a chamber 126, and a leaf valve 127 having one end overlying the port 128, port 12% providing for fluid communication between the variable capacity end chamber 131 and chamber 126. The end wall 124 also has a bore 129 of appropriate shape for placing the chamber 126 in fluid communica tion with the opposite end of the connecting line 121. An outlet line 134 at one end opens into the manifold chamber 126 and is connected to said manifold, and at the opposite end is connected to a reservoir (not shown) for retaining air under pressure. Mounted within the tubular housing is a piston assembly generally designated 133, said assembly including a connecting member 134 that includes a connecting rod and a diametrically enlarged cylinder portion 134:; at either end. Preferably the adjacent axial surfaces of the portions 13% are of a frusto-conical shape as described with reference to surfaces 42a, 43a of the first embodiment.

A piston 135 is attached to one end of the connecting rod and a piston 136 at the opposite end. The piston 135 includes Teflon seal ring 135a, an axial extending end member 1352'; that includes an end plate portion, an intermediate threaded portion and an end threaded portion as shown in FIGURE 8, and a retainer ring 135C that is threaded on said intermediate portion for retaining the Teflon seal in abutting engagement with said end plate portion. 'The threaded end portion is threaded into the connecting member. The piston 136 likewise includes a Teflon seal, an axially extending end portion and a retainer ring but of appropriately smaller diameters than the corresponding parts of piston 135. The diameter D of the seal 13541 is approximately the same as the inside diameter of the annular liner 113 that is mounted within the chamber 102.

An axially extending passageway 14-1 is formed in members 135a, 1351) and 135e, there being provided a leaf valve 142 having an end portion that overlies the outer axial opening of port 141. The opposite end of the leaf valve is secured to end plate portion 133!) at 143.

An annular liner 150 is provided in the tubular housing in bore 103, the inside diameter of liner 113 being one half that of liner 150. The variable capacity end chamber (cylinder chamber) 131 is the space enclosed by piston 136, liner 150 and end plate 12 while the chamber 114i is likewise bound by members 105, 113 and 135. The structure for reciprocating the piston assembly 133 in the tubular housing is the same as that described relative the first embodiment, the ball bearing of said drive structure being of a diameter to bear against the adjacent surfaces of the cylinder portions 134a of the connecting member 134. The piston assembly is reciprocated in the tubular housing equal axial distances in each of the lines 113 and 150.

Assuming that the piston assembly and drive members are located in a position correspondingly to that illustrated in FIGURE 1 and that the motor shaft is rotated in the direction of arrow 75 for the first embodiment, rotating the motor shaft in the aforemenitoned direction causes the pis'tondrive member to move the piston assembly in the direction of arrow 171. This compresses the air in the chamber 114 intermediate end wall 105 and seal 135a, leaf valve 142 blocking the passageway 141 so that the airintermediate the aforementioned members can not move back into the central chamber intermediate pistons 135 and 136. Upon air under pressure in chamber 114 building up above the pressure in chamber 108, the one end of the leaf valve 118 moves away from the port 107 to permit air to flow through said port and into chamber 108, and thence through line 121 to the bore 129 which opens into chamber 131, piston 136 at this time moving away from its adjacent end wall. The resulting pressure build up in chamber 131 causes leaf valve 127 to flex whereby air flows through the passageway 128 into chamber 126, provided the pressure in chamber 126 plus the force to open valve 127 is not greater than that of the pressure in chamber 131.

The rotation of the motor shaft to a position angularly in advance .ofithat corresponding to the FIGURE 6 position results in the piston assembly 133 being moved in the direction ofarrow 173. This results in the pressure in :chamber 114 decreasing sufliciently so that valve 113 closes and thereafter when the pressure has been decreased sufficiently below atmospheric, valve 142 opens to allow airflow through passageway 141 to chamber 11d.

In this connection bore 104 places the control interior portion of the tubular housing in fluid communication with the ambient atmosphere.

After pressure is built up in chamber 131 to be greater than that in chamber 126, due to assembly 133 moving in direction of arrow 173, the one end of the leaf valve 127 moves outwardly from passageway 128 to permit fluid flow into chamber 126. At the same time leaf valve 118 moves to block fluid flow through passage 107 while leaf valve 127 moves to permit fluid flow from chamber 131 and through passageway 12-8 to chamber 126. Air pressurized in chamber 126 is passed through the outlet line 134 to the reservoir. Since the diameter of piston 136 is twice that of piston 135, the outlet pressure in the outlet line is four times the pressure provided in the connecting line. Thus this unit serves as a double stage compressor.

It is to be understood that the second embodiment may utilize a replaceable metal sleeve and, Teflon seal ring and wiper ring in place of each of the annular rings if shoulders are provided, said members being of appropriate diameters and a piston assembly of FIGURE 3 is utilized other than that the diameter of one piston is twice the diameter of the other piston. Also the piston assembly of the first embodiment may be used in place of piston assembly 133 provided the pistons thereof are made of different diameters and the larger diameter piston is provided with a fluid passageway 141 and valve 142.

It is believed apparent from the above that axial portions of the pistons 42 and 43 are imperforated so that no fluid passageway is provided between bore 14 and the respective cylinder chambers.

In the event the pump unit 10 is .to be used as a vacuum pump, a line connected to boss 11a would be connected to container to be evacuated and the line 29 disconnected. Then as the piston assembly is moved in the direction of arrow 47 the valve 37 on wall 21would be flexed whereupon air would be drawn through bore 11d into the manifold inlet chamber and pass through passageway 21d into the cylinder chamber 31. At the end of the piston stroke the aforementioned valve 37 would block passageway 21d and when the piston assembly is moved in the direction of arrow 48, air is compressed sufficiently in chamber 31 to flex valve 34 so that air exhausts through passageway 21c and subsequently through boss 11d to the atmosphere.

As a further modification, each of the manifold chambers 27 may be provided with bores that open directly to the ambient atmosphere and no bore 11d .or boss 11:; provided. In such an event, the end walls would advantageously be provided with recesses for mounting valves 34 therein similarly as those provided for valves 37. With the thus modified pump .unit, .if it were desired to use it as a vacuum pump instead of as an air compressor, then, for example the end wall 21 would be angularly turned whereby passageway 21d served to place chamber 26 of plate 20 in fluid communication with cylinder chamber 31 and passageway 210.0penedto chamber 27 when valve 34 were flexed into chamber 27. End wall 23 would similarly be turned.

With reference to using a unit as a vacuum pump as described in each of the two preceding paragraphs, each of the fluid seal subassemblies is also turned end for end whereby each mounting sleeve radial flange would be adjacent the retainer ring and the sleeve 17 would abut against shoulder 15a. As a result, the wiper ring .portions 18a would be inclined in the opposite direction. It is to be understood that in order to facilitate this interchangeability, -the sleeves 16 and 17 are advantageously of approximately the same axial length andthe lengthof piston stroke and axial dimensions ofthe portions of the piston assembly are such that the wiper rings at all times form fluid seals with the pistons regardless if the unit is being used as a compressor or a vacuum'pump.

Although the valves have been described as leaf valves, it is to be understood that other types of conventional valves would be used as long as they performed the same function as described heretofore.

With reference to an example of the efliciency of the present compressor, his to be mentioned that prior art compressors now being built take A horse power motor to supply two cubic feet per minute at 20 pounds p.s.i. However, with the first embodiment air compressor of this invention, a one-twelfth horse power motor supplies two cubic feet at 20 p.s.i. As an example of the invention, this may be obtained with a motor running at 1050-1750 r.p.m. and a piston axial movement of 1 /2" to /2".

Further, prior art compressors will heat so hot that they cannot be run continuously at such a load. This is in contrast to the air compressor of this invention which has been run 24 hours a day for weeks at a time at such a pressure with no problem. The ability of this compressor to run continuously at such efficiencies and run at electric motor speeds without V-belts and other types of speed reduces markedly the size of air needed to obtain a given volume of air. This results in space and weight savings, which combine with small motors to make the entire unit much less expensive than compressors presently commercially available.

As many widely apparently different embodlments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein.

What we claim is:

1. In a pump unit, a housing having an aligned cylinder chamber at each axial end, a piston assembly in sa1d housing including a piston in each chamber and a connection rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, sa1d pistons having spaced, axially adjacent annular surface portions radially outwardly of said rod, drive means for bothrotating and axially reciprocating sa1d p stons in sa1d cylinder chambers, said drive means including a motor having a motor shaft and means mounted on sa1d motor shaft for bearing against said annular surface portions and cooperatnig therewith to rotate and reciprocate sa1d pistons as the motor shaft is rotated, the last mentioned means and motor shaft being located radially outwardly of said rod, and means at opposite axial ends of the housing for valving said chambers to draw fluid into one cylinder chamber and to exhaust a1r from the other chamber as the piston assembly is reciprocated in one axial direction and draw fluid into the said other chamber and exhaust fluid from said one chamber as the piston assembly is driven in the opposite axial direction.

2. In a pump unit, a housing having an aligned cyllnder chamber at each axial end, a piston assembly in said hous-' ing including a piston in each chamber and a connecting rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, said pistons having spaced adjacent axial surfaces, dr ve means for both rotating and axially reciprocating said pistons in said cylinder chambers, said drive means including a motor having a motor shaft that rotates about an axis about 90 relative the central axis of the piston assembly, a bearing having an outer race and an inner race and means for mounting said inner race on the motor shaft eccentrically relative the axis of rotation of the motor shaft and at a location that the outer race bears against said surfaces as the shaft is rotated, and means at opposite axial ends of the housing for valving said chambers to draw fluid into one cylinder chamber and to exhaust air from the other chamber as the piston assembly is reciprocated in one axial direction and draw fluid into the said other chamber and exhaust fluid from one said chamber as the piston as sembly is driven in the opposite axial direction.

3. The structure of claim 2 further characterized in that said outer race has a cylindrical outer peripheral surface, and that said axial surface-s comprise frustoconical surfaces that abut against said outer race surface,

one of said frusto-conical surfaces being inclined at substantially an 89 angle relative the piston assembly central axis and the other being inclined to be supplemental to said one frusto-conical surface.

4. in a pump unit, a housing having an aligned cylindri cal chamber at either axial end, a piston assembly in said housing including a piston in each chamber and a connecting rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, said housing having an'enlarged diametric portion at either axial end and means mounted in each enlarged diametric portion for forming a fluid seal with the adjacent piston, each of the fluid seal means including a fiirst sleeve of a resilient material, a second sleeve having a larger diameter than said first sleeve and located axially adjacent the respective outer axial end of the housing, and a wiper ring made of a somewhat resilient resinous material having a radially extending annular portion retained between said sleeves, and an inclined annular portion overlaying the second sleeve and having an inner circumfe ential edge bearing against the adjacent piston, drive means for both rotating and axially reciprocating said pistons in said cylinder chambers, and means at opposite axial ends of the housing for valving said chambers to draw fluid into one cylinder chamber and to exhaust air from the other chamber as the piston assembly is reciprocated in one axial direction and draw fluid into the said other cham: her and exhaust fluid from said one chamber as the piston assembly is driven in the opposite axial direction.

5. The structure of claim 4- further characterized in that said wiper ring is made of a polytetrafluoroethylene material.

6. A compressor unit comprising a housing having aligned cylinder chambers at opposite axial ends, a piston assembly in said housing including a piston in each chamber and a connecting rod of a small transverse dimension than the diameter of the pistons connecting said pistons, said pistons having spaced axially adjacent surfaces, drive means for reciprocating and rotating said pistons in the respective cylinder chamber, said drive means including a motor having a motor shaft rotated about an axis that extends nearly at a right angle to the directions of reciprocation of said pistons, a cam having a cylinder circumferential surface that abuts against the adjacent axial surfaces of said pistons and means for mounting said cam on the motor shaft eccentric to the axis of rotation of said motor shaft radially outwardly of the connecting rod and between the motor shaft and the connecting rod to bear against said adjacent axial surfaces and cooperate therewith to both rotate and reciprocate said pistons as the motor shaft is rotated, and means at opposite axial ends of the housing for valving said chambers and receiving air under compression to permit air intake into one cylinder chamber and compress air in the other chamber and deliver air under compression for use while the piston assembly is reciprocated in one axial direction and permit air intake in said other chamber and compress air in said one chamber as the piston assembly is driven in the opposite axial direction.

'7. The apparatus of claim 6 further characterized in that said cam mounting means includes a stud shaft mounted on the motor shaft eccentric to the axis of rotation of said shaft and that said cam comprises a bearing having an outer race and an inner race mounted on said stud shaft.

8. In a pump unit having a tubular housing, said housing having a diametrically enlarged bore portion at either axial end, a piston assembly reciprocally movable in said housing and including a connecting rod and a piston at each end of the connecting rod extending into the adjacent enlarged bore portion, means extendable into said housing for drivingly reciprocating said piston assembly, and means at opposite axial end portions of the housing acting in conjunction with adjacent piston moving in the housing for exhausting air from one cylinder chamber and drawing air into the other chamber while the piston assembly is being moved in one axial direction, and valving the intake and exhaustion of air, the improvement being a fluid seal subassembly mounted in each enlarged diametric portion to form a fluid seal with the adjacent piston, each subassembly includes a somewhat resilient resinous wiper ring having a generally radial annular portion and an inner annular portion joined to said radial annular portion, said inner annular portion having an inner circumferential edge that bears against the piston and annular means having an inner diameter that is of a larger diameter than the diameter of said inner circumferential edge for abutting against said radial annular portion to hold it against axial displacement as the respective piston is reciprocated.

9. The structure of claim 8 further characterized in that the last mentioned means includes a somewhat resilient sleeve abuttin against one axial surface of the wiper ring radial portion, a metal sleeve of a larger inside diameter than the resilient sleeve abutting against the opposite axial surface and a replaceable sleeve mounted in the housing enlarged diametric portion for retaining the resilient sleeve, Wiper ring and metal sleeve in the aforementioned relationship.

10. The structure of claim 8 further characterized in that the wiper ring is made of a polytetrafluoroethylene material.

11. The structure of claim 3 further characterized in that said drive means includes a motor having a motor shaft and means mounted on the motor shaft for simul taneously reciprocating and rotating the piston assembly as the motor shaft rotates.

12. In a pump unit, a housing having an aligned cylinder chamber at each axial end, a piston assembly in said housing including a piston in each chamber and a con nection rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, said pistons having spaced axially adjacent surfaces that together substantially form a supplemental angle relative the connecting rod axis, a shaft having an axis of rotation that extends at about one degree angle relative to a line of one of said axial surfaces that passes through the connecting rod axis, means mounted on said shaft for rotation therewith for hearing against said axial surfaces to rotatingly reciprocate said pistons, means to drivingly rotate said shaft abou its axis and means at opposite axial ends of the housing for valving said chambers to draw air into One cylinder chamber and to exhaust air from the other chamber as the piston assembly is reciprocated in one axial direction and draw air into the said other chamber and exhaust air from said one chamber as the piston assembly is driven in the opposite axial direction.

13. In a pump unit, a housing having an aligned cylinder chamber at each axial end, a piston assembly in said housing including a piston in each chamber and a connection rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, said pistons having spaced adjacent axial surfaces, drive means for axially reciprocating said pistons in said cylinder chambers, and means at opposite axial ends of the housing for valving said chambers to draw air into one cylinder chamber and to exhaust air from the other chamber as the piston assembly is reciprocated in one axial direction and draw air into the said other chamber and exhaust air from said one chamber as the piston assembly is driven in the opposite axial direction, said drive means including a drive shaft that rotates about an axis at an angle between 10 and .2" relative a line of one of said surfaces that passes through the piston assembly center axis, a cam, means for mounting said cam on the drive shaft eccentrically relative the axis of rotation of said shaft, and means for drivingly rotating said shaft about its axis, said cam mounting means mounting the cam for bearing against each of said surfaces to rotatably reciprocate said pistons as said shaft is rotated.

14. The apparatus of claim 13 further characterized in that said angle is between 15 and .5".

15. in a pump unit, a housing having an aligned cylinder chamber at each axial end, a piston assembly in said housing including a piston in each chamber and a connection rod of a smaller transverse dimension than the diameter of the pistons connecting said pistons, said pistons having spaced axially adjacent surfaces, the improvement comprising a driven shaft extending at an acute angle relative a straight line defined by the intersection of the plane of the piston assembly central axis and one of said surfaces and bearing means mounted on said shaft for bearing against each of said surfaces to both reciprocate and rotate said piston assembly as said driven shaft is rotated.

16. In a pump unit, a tubular housing having an aligned cylinder chamber at each axial end and a transverse bore intermediate said cylinder chambers, one of said cylinder chambers being of substantially larger diameter than the other, a piston assembly in said housing including a piston in each chamber and a connecting rod of a smaller transverse dimension than the diameter of the pistons connecting said piston, one of said pistons being of a cone spondingly larger diameter than the other and having an axially extending fluid passageway extending therethrough, drive means for both rotating and axially reciprocating said pistons in said cylinder chambers, and means at opposite axial ends of the housing for valvin-g said chambers to draw fluid into one cylinder chamber and to exhaust air from the other chamber as the piston assembly is reciprocatcd in one axial direction and draw fluid into the said other chamber and exhaust fluid from said one chamber as the piston assembly is driven in the opposite axial direction, each of the last mentioned means including a manifold plate having a fluid chamber and an outlet bore in fluid communication with the fluid chamber, an end wall intermediate the manifold plate and adjacent the axial end of the tubular housing, said end wall having a first fluid passage for placing the adjacent cylinderchamher in fluid communication with the respective manifold chamber, a valve on the end wall resiliently retained in a closed position to block fluid flow from said manifold chamber through said first passageway to .the adjacent cylinder chamber and permit fluid flow in the opposite direction, a second valve on the larger diametrie piston to permit fluid flow through the piston passageway when the last mentioned piston is moving toward the adjaqent end wall and block said piston passageway when the pistons are moving in the op osite direction, the end wall adjacent the smaller diameter cylinder chamber having a second fluid passageway opening to the last mentioned chamber, and a fluid conduit fluidly connecting said second fluid passageway to the manifold outlet bore on the opposite axial end of the housing.

17. A compressor unit comprising a tubular housing having aligned cylinder chambers at opposite axial ends, a piston assembly in said housing including a piston in each chamber and a connecting rod of a small transverse dimension than the diam-eter of the pistons connecting saidpisto-ns, said pistons having spaced axially adjacent surfaces, drive means for reciprocating said pistons in the respective cylinder chamber, said drive means including a motor having a motor shaft rotated about an axis that extends nearly at a right angle to the direction of reciprocation of said pistons, a cam havinga cylindrical surface that abuts against the adjacent axialsurfaces of said pistons and means for mounting said cam on the motor shaft eccentric to the axis of rotation of said motor shaft and between the motor shaft and the connecting rod, and means at opposite axial ends of the housing for valving said chambers and receiving air under compression to permit air intake into one cylinder chamber and compress air in the other chamber and deliver air under compression for use while the piston assembly is reciprocated in one axial direction and permit air intake into said other chamber and compress air in said one chamber as the piston assembly is driven in the opposite axial direction, said tubular housing including means in either axial end of the housing to form a fluid seal with the respective piston, said fluid seal means each including a wiper ring of somewhat resilient resinous material having a radial extending annular portion and an inclined annular portion that has an inner peripheral edge that bears agaist respective piston and means bearing against the first men tioned annular portion for replaceably holding it against axial displacement as the pistons are reciprocated.

References (Zitezli by the Examiner UNITED STATES PATENTS Re. 19,210 6/1934 Tursky 23G185 1,130,959 3/1915 Campbell 230185 1,371,824 3/1921 Tursky 230-173 FOREIGN PATENTS 1,033,552 4/1953 France.

0 DONLEY J. STOCKING, Primary Examiner.

WARREN E. COLEMAN, LAURENCE V. EFNER,

Examiners. 

1. IN A PUMP UNIT, A HOUSING HAVING AN ALIGNED CYLINDER CHAMBER AT EACH AXIAL END, A PISTON ASSEMBLY IN SAID HOUSING INCLUDING A PISTON IN EACH CHAMBER AND A CONNECTION ROD OF A SMALLER TRANSVERSE DIMENSION THAN THE DIAMETER OF THE PISTONS CONNECTING SAID PISTONS, SAID PISTONS HAVING SPACED, AXIALLY ADJACENT ANNULAR SURFACE PORTIONS RADIALLY OUTWARDLY OF SAID ROD, DRIVE MEANS FOR BOTH ROTATING AND AXIALLY RECIPROCATING SAID PISTONS IN SAID CYLINDER CHAMBERS, SAID DRIVE MEANS INCLUDING A MOTOR HAVING A MOTOR SHAFT AND MEANS MOUNTED ON SAID MOTOR SHAFT FOR BEARING AGAINST SAID ANNULAR SURFACE PORTIONS AND COOPERATING THEREWITH TO ROTATE AND RECIPROCATE SAID PISTONS AS THE MOTOR SHAFT IS ROTATED, THE LAST MENTIONED MEANS AND MOTOR SHAFT BEING LOCATED RADIALLY OUTWARDLY OF SAID ROD, AND MEANS AT OPPOSITE AXIAL ENDS OF THE HOUSING FOR VALVING SAID CHAMBERS TO DRAW FLUID INTO ONE 